RC Drag Racing Christmas Tree and Speed Trap

In the drag racing world, a Christmas tree is the post at the start line that sequentially lights up a set of yellow lights followed shortly after by a green light to tell the drivers to go, the lights obviously giving it its seasonal name. Included at the base of the tree are lasers to detect the presence of the cars.

[Mike] not only made his own Christmas tree for his RC cars, but he even made an end-of-track circuit with LED displays telling the cars how long they took. Both start and finish hardware are controlled by Pololu Wixel boards which has TI CC2511F32 microcontrollers with built-in 2.4 GHz radios for wireless communications.

In addition to the LEDs, the Christmas tree has a laser beam using a 650nm red laser diode for each car at the start line that’s aimed at a TEPT5600 phototransistor. If a car crosses its beam before the green light then a red light signals the car’s disqualification.

The end-of-track circuit has 7-segment displays for each car’s time. [Mike] designed the system so that the Christmas tree’s microcontroller tells the end-of-track circuit’s microcontroller when to reset the times, start the times, and clear the times should there be a disqualification. The finish line controller has lasers and phototransistors just like the starting line to stop the timers.

Oh, and did we mention that he also included 1980’s car racing game sounds? To see and hear it all in action check out the video after the break. If the cars seem a little drunk it’s because pushing left or right on the controller turns the wheel’s fully left or right.

10 thoughts on “RC Drag Racing Christmas Tree and Speed Trap

  1. Awesome project! I’m picture a v2 of this where there’s a set of spaced optos per lane at the finish line that enable the micro to do an “mph/kmph” calculation & display… once the capability is there, the user could adjust for real speed or scale speed however they wished.

    Thanks for posting this & kudos to [Mike]!

  2. Nice project! I had just begun designing a low cost christmas tree for a local dirt drag track. They have been using a three light tree and some switches to a car battery. I’m sure we can do much better at a reasonable cost these days. The staging lines and speed trap are going to be a challenge with all the dirt though.

  3. I totally misunderstood this title.

    I though it was an RC Christmass Tree that did the drag racing. As in a yule tide holiday pine tree on wheels that zoomed in a straight line down the street.

    Which would be … epic.

    Link that up with the the LEDs so that the faster it goes the more red the lights get ( you know, red shift and all that)…..

  4. Has anyone done a home built timing system for RC cars? There was a US built system out there that Kyosho bought up and made too expensive for individuals to run. Surely someone has made one?

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